1. Field of the Invention
This invention relates to apparatus for bending bar-shaped, plastically-workable materials such as metal rods and pipes.
2. Description of the Prior Art
Heretobefore the operation of bending bar-shaped materials has been made manually with the help of a pair of spaced-apart studs projecting from a base plate. That is, one end of the material is positioned between the studs, and its other end is manually turned about the studs to bend the material. Among the problems of such a conventional technique is that the material often cannot be bent in exact accordance with the predetermined radius of curvature or at the exact predetermined position.
In order to solve such prior art problems has been proposed a bending apparatus wherein a bender means is coupled to a rotatable shaft having a sprocket. A chain is fitted onto the sprocket and an output shaft of a geared motor. The bender means has a circular shape, and a material to be bent is pressed against the periphery thereof with a suitable clamp means and the shaft is rotated to bend the material along said periphery. In such a proposal, however, if a large-sized sprocket is used, the forward portion of the work that moves as the bender means is rotated (portion of the work that is forward of its portion held by the presser means and clamp means) may strike against the sprocket to prevent the bending operation. Such a situation is often encountered where a bar-shaped material is to be successively bent at a number of sections thereof in its lengthwise direction. Furthermore the shaft of the apparatus constructed as above must be thick. The rotable shaft is subject to large tortional stress when the torque applied to the sprocket is transmitted through the rotatable shaft to the bending support. The rotable shaft must have a thickness sufficient to withstand such large tortional stress. When a thick rotable shaft is used, the bending work support to be mounted on the rotable shaft must be of a large diameter suitable for mounting on the thick rotable shaft. A bending work support of small diameter can not be used.
Apparatus of the following construction has been devised to eliminate the problem in which the sprocket obstructs the bending operation against the work. To one end of the rotable shaft is connected one end of a lever, to the other end of which is connected a driving means such as a hydraulic cylinder through a linkage. With the apparatus of this type, bending processes can be performed with ease on slender work successively along the longitudinal direction thereof at two, three or more portions, since the apparatus lacks the obstructive sprocket. During the bending process, the driving force of the driving means is conveyed to the rotable shaft through the cylinder and the lever, and further to the bending work support via the rotable shaft. Accordingly, a rotable shaft is necessary which is sufficiently thick to withstand the large tortional stress as in the case of the apparatus with the sprocket. Consequently a usable bending work support is limited to one of a large diameter which is adaptable to the thick rotable shaft as described previously.